यदग्ने रोहितंरूपं तेजसस्तद्रूपं यच्छुक्लं तदपां यत्कृष्णं तदन्नस्यापागादग्नेरग्नित्वं वाचारम्भणं विकारो नामधेयं त्रीणि रूपाणीत्येव सत्यम् ॥ ६.४.१ ॥
yadagne rohitaṃrūpaṃ tejasastadrūpaṃ yacchuklaṃ tadapāṃ yatkṛṣṇaṃ tadannasyāpāgādagneragnitvaṃ vācārambhaṇaṃ vikāro nāmadheyaṃ trīṇi rūpāṇītyeva satyam || 6.4.1 ||
1. The red colour of gross fire is from subtle fire, the white colour is from subtle water, and the dark colour is from subtle earth. Thus that which constitutes the ‘fire’-ness of fire is gone. All changes are mere words, in name only [i.e., fire is only a name indicating a certain condition]. The three colours are the reality.
Word-for-word explanation:
Yat agneḥ rohitam rūpam, that red colour of [gross] fire; tat rūpam tejasaḥ, that colour is from [subtle] fire; yat śuklam, that which is white; tat apām, that is from [subtle] water; yat kṛṣṇam, that which is dark; tat annasya, that is from [subtle] earth [lit., food]; agneḥ agnitvam apāgāt, [thus] the ‘fire’-ness of fire is gone; vācārambhaṇam nāmadheyam vikāraḥ, all changes are mere words, in name only; trīṇi rūpāṇi iti eva satyam, only the three colours are the reality [i.e., outside of the three colours, there is no fire].
Commentary:
When fire is gross it has a red colour which comes from its subtle aspect. But there is also a white colour in it which comes from the subtle water element. Similarly, sometimes it has a dark colour which comes from the subtle earth element. The Upaniṣad says, in reality, fire is nothing beyond these three colours—red, white, and black. This proves the falsity of the idea of gross fire.